The present invention relates generally to control and monitoring networks, such as those used in industrial applications. More particularly, the invention is directed to techniques associated with powering and facilitating communication between multiple networked devices in a control and monitoring system.
A control and monitoring system may include a device or set of devices that monitor and/or manage the behavior of other devices of a system. Indeed, a control and monitoring system may essentially act as a nerve center for a system. For example, in many industrial and commercial applications, a device, such as a programmable controller or computer, may send and receive signals over a network to operate and/or monitor a wide range of motors, valves, actuators, sensors, and the like. It should be noted that a control system may include one or more individual controllers, computers, and so forth, in a single location or remote locations. In other words, the control system may be centrally located or distributed throughout the system. Indeed, the control system may be integrated into various networked components that collectively define the control system.
A control and monitoring system typically utilizes a network to facilitate communication between various industrial devices, such as sensors and actuators, and higher-level devices, such as programmable controllers and computers. A range of networks and corresponding protocols are known and are presently available to facilitate control and monitoring operations. For example, DeviceNet, which is based on controller area network (CAN) technology, is an open device level network developed by Rockwell Automation that uses common industrial protocol (CIP) to provide the capability to control, configure, and collect data for many available industrial devices.
Control system networks include certain physical components or features that facilitate proper operation and communication. For example, a control system network may include various conductors to facilitate transmission of power and data signals between components of the network. In other words, various devices of a control system may be communicatively coupled to one another via such conductors. A typical data system, such as for the DeviceNet protocol, includes a ground conductor, a power conductor, and a pair of data conductors. In some systems, each of these conductors may be provided as a single cable. For example, the various conductors may be provided within a single sheath that defines the outer portion of a cable, or the various conductors may be sheathed separately and bundled together as a single cable to efficiently provide each of their various functions throughout a system.
The power conductor in a control system network supplies various devices of the control system network with power from one ore more power supplies. A power supply may receive power originating from a power source, such as a power grid, at an initial power level and convert the power to an operable power level. For example, a particular power supply may receive power from a 110 VAC source, convert the 110 VAC to 24 VDC, and supply a plurality of devices with the 24 VDC to facilitate operation of each of the devices. However, a single power supply may be limited in its ability to provide sufficient power under certain circumstances. Indeed, due to voltage losses, a single power supply may not be able to provide power over long distances. For example, if several devices are substantially spaced apart on a power conductor, the power supply may not be able to efficiently power all of the devices because of voltage losses over the length of the power conductor. Similarly, a single power supply may not be capable of powering a large number of devices. Accordingly, it is often desirable to utilize multiple power supplies in a single network to provide sufficient power while maintaining communication between the networked devices.
While the inclusion of multiple power supplies may facilitate the operation of systems including numerous devices and/or systems including long cable lengths, inclusion of multiple power supplies may also be associated with various inefficiencies. For example, including extra power supplies in a network can be expensive. Further, multiple power supplies can cause accessibility issues when they are located a great distance from one another.